Please explain what you are really trying to do. You cannot amend a W-2. A W-2 is a tax document issued to you by an employer--you cannot change it yourself. Did you file a tax return and forgot to enter a W-2--and now do you need to amend the tax return to include that W-2? Or did you enter it incorrectly? Provide some details.
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As xmasbaby0 mentioned, you cannot amend a form W2, if your form W2 needs to be corrected, you need to contact your employer so that they can issue a corrected W2.
If you need to add a W2 form or correct a form W2 that you entered incorrectly on your return, then you will need to amend your return.